1. Field of the Invention
The invention relates to a magnetic data writing apparatus called a “disk servo writer”, for writing servo patterns for detecting magnetic head positions, writing ID patterns for identifying disks, and writing programs into magnetic disks that initially contain no data, to produce magnetic disk products including data written therein upon requests of clients. Hereinafter, the magnetic data writing apparatus will be referred to as the “disk servo writer.”
Specifically, the invention relates to a disk servo writer for stacking a plurality of magnetic disks (hereinafter referred to as “copy disks”), to which magnetic data is to be transferred, and a magnetic disk (hereinafter referred to as an “original disk”) storing the magnetic data to be transferred to the copy disks and/or the magnetic data referred to in writing data to the copy disks. The disk servo writer rotates the copy disks and the original disk concentrically (around a common axis), and simultaneously writes onto the copy disks the magnetic data determined on the basis of the data read out from the original disk. The data to be written is read out via a magnetic head used solely for reading out data the respective copy disks via multiple sets of magnetic heads (hereinafter referred to as “servo heads”). Each set of magnetic heads includes a plurality of servo heads arranged on the recording surface of the respective copy disk.
More specifically, the invention relates to a method of obtaining head positions in a magnetic data writing apparatus (disk servo writer) for easily obtaining the relative position address relationships between the read-only head and the servo heads in advance, to cause the servo heads on the recording surface of a copy disk to write data correctly into the respective track ranges to which the servo heads are assigned.
2. Prior Art
Recently, recording densities of the hard disk drives have been increasing continuously to realize small magnetic storage devices with high storage capacities. To realize higher recording densities, the tracking servo technique for the magnetic heads for writing and reading data plays important roles.
According to the conventional tracking servo technique, tracking servo signals, address signals (track addresses, sector addresses), clock signals and such data signals, are formatted and recorded in the form of servo patterns in the magnetic recording media (magnetic disks). The magnetic head reads out these data signals, checks the position thereof based on the data signals read out, and corrects the position thereof to scan the tracks accurately.
One of the means for recording the servo patterns in the magnetic disks is a disk servo writer, which stacks a plurality of magnetic disks, employs one of the magnetic disks as an original disk, stores the servo data in the original disk in advance, and copies the servo patterns formed, from the servo data in the original disk to the other magnetic disks via magnetic heads.
Now a conventional disk servo writer will be described below with reference to FIGS. 9 through 11, wherein the same reference numerals are used to designate the same or corresponding constituent elements. FIG. 11 is a top plan view of a magnetic disk 4 schematically showing regions PS2 (hereinafter referred to as “servo pattern regions”), in which servo patterns are stored, and regions DTA (hereinafter referred to as “data regions”), in which data is stored. Servo pattern regions PS2 are arranged radially at every same number of degrees of angle, that is, at a sector interval. Servo pattern regions PS2 and data regions DTA are on both major surfaces of magnetic disk 4. In the following, the reference symbol PS2 is used also to designates servo patterns and the reference symbol DATA also to designate data.
Data regions DTA are the regions in which the foregoing ID patterns and programs are written by a disk servo writer at the requests of the client, or the regions in which data is written by the user of magnetic disk 4. FIG. 9 is a block diagram schematically showing a conventional disk servo writer. A disk servo writer of a similar kind is disclosed in Japanese Unexamined Laid Open Patent Application 2001-216750.
Referring now to FIG. 9, a disk servo writer 101 mounts a disk stack unit 5 stacking multiple (nine in the figure) magnetic disks (copy disks) 4, in which data is to be written, and a clock pattern disk 3K below disk stack unit 5. The disks are mounted on the shaft of a spindle motor so that disk stack unit 5 and clock pattern disk 3K may be rotated simultaneously at a high speed of rotation.
Clock pattern disk 3K is obtained by writing clock patterns PCO in the outermost circumference section of a magnetic disk as shown in FIG. 10 with disk servo writer 101. The clock patterns PCO are written in advance of writing servo patterns PS2 to the other copy disks 4. Then, servo patterns PS2 are written into the copy disks 4, synchronizing with the clocks obtained by reading out clock patterns PCO.
Also shown in FIG. 9 is a clock head 10K for writing and reading clock patterns PCO directly to and from clock pattern disk 3K, a clock head positioner 2K for supporting clock head 10K and for positioning clock head 10K in the outermost circumference section of clock pattern disk 3K, and a clock pattern generator 9K for generating the signals of clock pattern PCO to be written into clock pattern disk 3K. Servo heads 10 are magnetic heads arranged in one-to-one correspondence to the respective surfaces of M copy disks 4, for writing servo patterns PS2 directly to the respective surfaces of copy disks 4. A rotary positioner 2 is provided for stacking the servo heads 10 and for rotating them around an axis 2s to move them to the desired radial positions on the respective copy disks 4. An encoder 20 is arranged in a coaxial manner with rotary positioner 2 for detecting the rotating position of rotary positioner 2. A position detector 21 obtains the positions (analog values) of servo heads 10 in the radial direction of the magnetic disk from the rotating position detected by encoder 20.
A servo compensator 12 and a power amplifier 13 constitute, together with encoder 20 and position detector 21, a feedback loop for controlling via rotary encoder 2 the positioning of servo heads 10 in the radial direction of the respective disks, that is the positioning of servo head 10 on the radial position in the center of the desired track.
The difference between the reference position ρS of each servo head 10 (the analog value corresponding to the radius of the center of the target track) and the detected head position ρ, which is the actual radial position outputted from position detector 21, is inputted to servo compensator 12. Servo compensator 12 amplifies the inputted difference and calculates a servo compensation value that minimizes the difference. Power amplifier 13 outputs a current for driving rotary positioner 2 based on the servo compensation value to move the servo heads 10. A servo pattern generator 9, to which the clock is inputted from clock head 10K and the detected head position ρ is inputted from position detector 21, generates servo patterns PS2 and causes servo heads 10 stacked on rotary positioner 2 to write the servo patterns PS2 to the respective copy disks 4.
Now the entire functions of the conventional disk servo writer shown in FIG. 9 will be described. First, clock head 10K stores clock patterns PCO generated from clock pattern generator 9K at an arbitrary radial position (the outermost circumference section in FIG. 10) on clock pattern disk 3K.
Then, the actual radial position p of the servo heads 10 is detected by rotary encoder 20 arranged in a coaxial manner with rotary positioner 2 and position detector 21. The error (difference) between the detected head position ρ and the reference head position ρS is fed back through servo compensator 12 and power amplifier 13, and servo head 10 is caused to track the reference head position ρS via the rotary positioner 2.
In the tracking state, servo heads 10 simultaneously write the servo patterns PS2 generated by the servo pattern generator 9, to the surfaces of the respective copy disks 4, synchronizing with the clock read out from clock pattern disk 3K via clock head 10K. The servo pattern generator 9 is provided with means (not illustrated in the drawings) that outputs data such as ID data and programs to servo heads 10, synchronizing with the clock from clock pattern disk 3K and that causes the servo heads 10 to write the data and the programs to data regions DTA on the copy disks 4.
Other related prior art patent publications describe other known techniques related to writing onto magnetic disks. Thus, Japanese Unexamined Laid Open Patent Application H10 (1998)-172254 and Japanese Unexamined Laid Open Patent Application H03 (1991)-214474 disclose methods for writing servo data to magnetic disks, including the step of selecting a master surface from the recording surfaces of magnetic disks, the step of writing a master servo pattern onto the master surface in a hard disk drive, and the step of writing servo patterns onto the recording surfaces other than the master surface while positioning the magnetic heads based on the master servo pattern. Japanese Unexamined Laid Open Patent Application H06 (1994)-44711 discloses a method for simultaneously writing servo patterns on the recording surface of a magnetic disk with a plurality of magnetic heads in a disk servo writer. Japanese Unexamined Laid Open Patent Application H06 (1994)-60545 discloses the method for simultaneously writing servo data to a plurality of magnetic disks in a hard disk drive based on the signals from an external servo writer. Japanese Unexamined Laid Open Patent Application H06 (1994)-28793 discloses the method for compensating off-track in a hard disk drive.
As described above, the conventional disk servo writers write the servo patterns generated by a servo pattern generator simultaneously to stacked magnetic disks, sy with the clock patterns recorded in advance in a clock pattern disk. Therefore, the amount of time for writing the servo patterns to the entire surfaces of all the disks in a disk stack unit is given by (the time for on revolution of the disk)×(the number of tracks, to which the servo patterns are written).
As the track density on a magnetic disk is improved, the time for servo pattern writing becomes longer, causing lower throughput. Although it is possible to shorten the time for servo pattern writing by increasing the rotational speed of the disks, there is a tradeoff between shortening the writing time by faster disk rotation and mechanical vibrations that become more vigorous with the increased speed and make it harder to write the servo patterns accurately.
Of course, the throughput is improved by increasing the number of the magnetic disks stacked. However, the accuracy of the spindle motor rotation is impaired by increasing the number of disks in the stack since a heavier load is exerted on the spindle motor. Thus, it becomes increasingly difficult to mount the magnetic heads within the predetermined range of accuracy, as the number of stacked magnetic heads increases.
A method for avoiding these problems, and for shortening the servo pattern writing time has been proposed. The method includes stacking on the shaft of a spindle motor an original disk storing servo data as a base of servo patterns and a plurality of copy disks, arranging a plurality of servo heads on each surface of the copy disks, and causing the servo heads to write the servo patterns formed based on the servo data read out by a read-only head from the original disk to the respective track ranges assigned to the respective servo heads.
However, since the displacements between the read-only head on the original disk and a plurality of the servo heads on the surface of each copy disk are different from servo head to servo head, the servo patterns written in may be displaced. To prevent the servo pattern displacement from occurring, it is necessary to accurately detect the positional relationships between the read-only head and the servo heads in advance, and to correct the displacements prior to writing the servo patterns via the servo heads. However, it takes time to detect the positions of the magnetic heads. Therefore, it is necessary to obviate this problem.